Standardize usage of virtual/override/final in extensions/

extensions/common/manifest_handlers/background_info.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef EXTENSIONS_COMMON_MANIFEST_HANDLERS_BACKGROUND_INFO_H_
 #define EXTENSIONS_COMMON_MANIFEST_HANDLERS_BACKGROUND_INFO_H_
 
 #include <string>
 #include <vector>
 
 #include "base/values.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/manifest_handler.h"
 #include "url/gurl.h"
 
 namespace extensions {
 
 class BackgroundInfo : public Extension::ManifestData {
  public:
   BackgroundInfo();
-  virtual ~BackgroundInfo();
+  ~BackgroundInfo() override;
 
   static GURL GetBackgroundURL(const Extension* extension);
   static const std::vector<std::string>& GetBackgroundScripts(
       const Extension* extension);
   static bool HasBackgroundPage(const Extension* extension);
   static bool HasPersistentBackgroundPage(const Extension* extension);
   static bool HasLazyBackgroundPage(const Extension* extension);
   static bool HasGeneratedBackgroundPage(const Extension* extension);
   static bool AllowJSAccess(const Extension* extension);
 
@@ skipping 42 matching lines @@
   // Defaults to true.
   bool allow_js_access_;
 
   DISALLOW_COPY_AND_ASSIGN(BackgroundInfo);
 };
 
 // Parses all background/event page-related keys in the manifest.
 class BackgroundManifestHandler : public ManifestHandler {
  public:
   BackgroundManifestHandler();
-  virtual ~BackgroundManifestHandler();
+  ~BackgroundManifestHandler() override;
 
-  virtual bool Parse(Extension* extension, base::string16* error) override;
-  virtual bool Validate(const Extension* extension,
-                        std::string* error,
-                        std::vector<InstallWarning>* warnings) const override;
-  virtual bool AlwaysParseForType(Manifest::Type type) const override;
+  bool Parse(Extension* extension, base::string16* error) override;
+  bool Validate(const Extension* extension,
+                std::string* error,
+                std::vector<InstallWarning>* warnings) const override;
+  bool AlwaysParseForType(Manifest::Type type) const override;
 
  private:
-  virtual const std::vector<std::string> Keys() const override;
+  const std::vector<std::string> Keys() const override;
 
   DISALLOW_COPY_AND_ASSIGN(BackgroundManifestHandler);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_MANIFEST_HANDLERS_BACKGROUND_INFO_H_